The disclosure relates to a light source unit and an optical engine. In particular, the invention relates to a light source unit that utilizes emission of light derived from phosphor, and to an optical engine provided with the light source unit.
A discharge-based light source such as an ultrahigh pressure mercury lamp or a xenon lamp has been used for a projector. In recent years, a configuration has been proposed in which light-emitting diodes (LEDs) are used for a light source (for example, see Japanese Unexamined Patent Application Publication No. 2011-2518) or in which a semiconductor laser element is used for a light source (for example, see Japanese Unexamined Patent Application Publication No. 2012-88451), in terms of superiority in decreased power consumption and a reduced environmental burden.
In particular, high expectation is placed, as a high luminance projector that takes safety into consideration, on a hybrid projector in which a semiconductor laser element and a phosphor are combined (for example, see Japanese Unexamined Patent Application Publication Nos. 2011-13313, 2011-76781, 2012-63488, and 2004-341105). For example, a light source unit of a projector disclosed in JP2011-13313A is provided with a blue semiconductor laser element and a rotatable phosphor wheel. The phosphor wheel includes a wheel substrate serving as a circular substrate formed with three regions that are adjacent to one another in a circumferential direction and each having a fan-like shape. The wheel substrate includes: a region in which a phosphor that absorbs blue light and emits green light is arranged; a region in which a phosphor that absorbs the blue light and emits red light is arranged; and a transparent base material region in which a light diffusion layer is arranged instead of a phosphor. The phosphor wheel disclosed therein is thus a so-called reflective phosphor wheel. In the light source unit, the blue light emitted from the blue semiconductor laser element is condensed by a lens to be applied onto the phosphor wheel while the phosphor wheel is in rotation. The blue light thus passes through the phosphor wheel when being applied onto the transparent base material region, and causes the green light or the red light to be emitted and reflected toward the blue semiconductor laser element when being applied onto one of the regions arranged with the respective phosphors. The laser light having passed through the phosphor wheel and the pieces of light having been emitted from the respective phosphors are used as illumination light. Further, those pieces of color light are time-divisionally displayed by a display device located downstream of the light source unit on the basis of image data, thus allowing a color image to be formed on a screen.
Also, a light source unit of a projector disclosed in JP2004-341105A is provided with a blue-violet light excitation light source and a rotatable phosphor wheel, for example. The phosphor wheel includes a wheel substrate serving as a transparent substrate in which a phosphor that emits blue light, a phosphor that emits green light, and a phosphor that emits red light are coated in a circumferential direction on a light exiting side of the transparent substrate to define respective three regions. The phosphor wheel is thus a so-called transmissive phosphor wheel. In the light source unit, blue-violet light is applied onto the phosphor wheel while the phosphor wheel is in rotation, causing the red light, the blue light, and the green light to be emitted on the opposite side of the excitation light source from the respective phosphors.
Incidentally, when utilizing the light emitted from the phosphor for part or all of illumination light, it is necessary to use an excitation light source having a high light intensity in order to achieve higher luminance. Such a high-light-intensity light source unit is achieved by arranging a plurality of semiconductor laser elements.
For example, a light source unit of a projector disclosed in JP2011-76781A is provided with a plurality of blue laser emitters arrayed in matrix, a rotatable phosphor wheel, and a red LED. The phosphor wheel includes a wheel substrate in which a phosphor-arranged region and a transparent base material region are disposed side-by-side in a circumferential direction. The phosphor-arranged region is arranged with a phosphor that emits green light, and the transparent base material region is arranged with no phosphor and includes a light diffusion layer. The phosphor wheel disclosed therein is thus a reflective phosphor wheel. In the light source unit, the blue light emitted from each of the blue laser emitters is caused to be parallel light by a collimator lens before being applied onto the phosphor wheel, while the phosphor wheel is in rotation. Thus, the blue light that passes through the phosphor wheel upon application of the blue laser light onto the transparent base material region, the green light reflected upon application of the blue laser light onto the phosphor-arranged region, and the red light emitted from the LED form illumination light.
Also, for example, a light source unit of a projector disclosed in JP2012-63488A is provided with a plurality of blue light sources each generating blue light that serves both as excitation light and color light, and a transparent substrate that holds a phosphor layer thereon. The plurality of blue light sources are disposed in five-row-five-column matrix pattern on a substrate. The transparent substrate is fixed at a predetermined position, and the phosphor layer is disposed on a light exiting side of the transparent substrate. The phosphor layer produces fluorescence that includes red light and green light from part of the blue light that have entered the transparent substrate, and remaining part of the blue light passes through the phosphor layer, thus forming illumination light.